Global planning for dexterous reorientation of rigid objects: Finger tracking with rolling and sliding

We address global motion planning for quasi-static reorientation of convex objects (polyhedral and smooth objects) with a four-fingertip grasp. We mak e use of a simple humanlike manipulation strategy in which a single finger is moved at each instant while the other three are maintained fixed (with r egard to the palm)-an extended version of the original finger-tracking sche me of Rus. This new version essentially incorporates frictional rolling and sliding at the fingertips and deals with the related contact kinematics an d quasi-static motion/force prediction issues. Our contribution is twofold. First, we describe an analysis showing that this extended scheme is suitab le for reducing the space of the object motions, thereby making motion plan ning easier and operating on a search space of low dimension. Our second co ntribution is a planner that exploits such a search space reduction and app lies the extended finger tracking at the core of a multilevel hierarchical framework to search for global reorientation trajectories. The planner has been implemented and used for achieving several nontrivial frictional reori entation tasks that show the capabilities and the promise of our approach.